Researchers have noticed that people who lived high in Argentina's Andes Mountains for hundreds of years have been exposed to high levels of arsenic, which naturally occurs in their water.

Arsenic is a deadly chemical which can cause cancer and is mainly deadly for children and obstructs people's ability to reproduce.

During the study, published in the journal Molecular Biology and Evolution, researchers found that different people had different ability to metabolize and get rid of this fatal chemical.

In order to figure out the reason behind the variation, the researchers analyzed the genes which are a part of this detoxification process.

They did the comparison between the genetic fingerprint of the people whose children hailed from this area and those from South American environs home to drinking water with lower levels of arsenic.

The scientists found that natives of the high-arsenic area had a genetic variation that is connected with an ability to metabolize more quickly and get rid of the substance.

Karin Broberg, study author, a researcher at the Karolinska Institute in Sweden, said that this is the first proof of human adaptation to toxic material.

According to Broberg, the researchers assumed that people who showed this genetic variation had higher chances of survival and thus passed on this trait.

The studies done in the past have shown that people who have this genetic fingerprint metabolize arsenic differently from others, and get rid of the metalloid faster, by converting it into a substance known as dimethylarsinic acid.

The past studies have also revealed that the ones didn't have this genetically derived ability are more prone to metabolizing arsenic into a chemical called monomethylarsonic acid. This acid is comparatively more deadly and takes a lot of time to remove from the body.